(Revised Abstract) Description: The ascertainment of millions of SNPs in the human genome, characterization of haplotype blocks and development of improved SNP-based linkage panels has fueled the need for accurate, efficient, and low cost SNP genotyping technologies to support genetic inheritance and disease association studies. The overall goals of this proposal are to develop and test a novel method for multiplex genotyping using in-gel polony amplification and fluorescence in situ sequencing. In Phase I, the core genotyping technology will be tested using a set 372 SNPs from The SNP Consortium (TSC) linkage panel with known genotypes on individuals from the CEPH families. Genotypic data will be collected from 48 unrelated CEPH individuals and evaluated in terms of success rate and accuracy. The cost competitiveness of the technology relative to other established genotyping technologies will then be evaluated.